Assessing the quality of concrete – reinforcement interface in Self Compacting Concrete

Research has shown that even self-compacting concrete (SCC) mixtures can exhibit the so-called “top-bar effect” which impacts bond and anchorage. Several instances of conflicting results have nevertheless been published regarding interfacial bond between self-compacting concrete and steel reinforcement. The scope of this paper is to present an experimental methodology for assessing the quality of the interface between self-compacting concrete and ribbed reinforcement. For this purpose, seven different self-compacting and four normally vibrated concrete (NVC) mixtures with diverse rheological characteristics were examined. Digital Image Analysis of cut sections containing reinforcing bars at different cast-heights was used as a diagnostic tool. The study illustrates that the quality of the interface is strongly affected by the viscosity of the SCC mixtures and by the slump values in NVC. Self-compacting concrete mixtures show greater inherent robustness and cohesion at the steel–concrete interface compared to conventionally vibrated concretes.